A nondestructive testing method using radiation has been used in a wide range of fields from industrial applications to medical applications.
For example, the X-ray refers to an electromagnetic wave with a wavelength of about 1 pm to 10 nm (10−12 to 10−8 m). Of them, the X-ray with a short wavelength (about 2 keV or more) is referred to as a hard X-ray, and the X-ray with a long wavelength (about 0.1 keV to about 2 keV) is referred to as a soft X-ray.
For example, there is known an absorption contrast method of obtaining an absorption image using a difference in transmittance when an X-ray is transmitted through an object. The method using a high X-ray transmittance has been practically used for an internal crack inspection of an iron and steel material and an application in a security field such as a baggage inspection.
Meanwhile, when the object is made of substances with a density difference too small to detect a change in contrast by X-ray absorption, X-ray phase contrast imaging is effective in detecting an X-ray phase shift through the object. For example, the X-ray phase contrast imaging is expected to be applied to imaging of a polymer blend and a medical application.
Of the various X-ray phase contrast imaging methods, the method disclosed in PTL 1 is very simple and effective in using a refraction effect to detect a phase shift through the X-rayed object. Specifically, the method is such that an X-ray source with a micro focus is used; the object and the detector are spaced away from each other; and thereby, the object is detected with its edge enhanced due to the refraction effect through the X-rayed object.
In addition, unlike many X-ray phase contrast imaging methods, the method of using the refraction effect is characterized in that a high coherence X-ray beam such as a synchrotron radiation beam is not always required.
Meanwhile, PTL 2 discloses an imaging apparatus installing an X-ray shielding mask in an edge portion of a pixel of the detector.
In the absence of the object, when setting is performed in such a manner that an X-ray is emitted to part of the shielding mask, an X-ray positional change due to the object refraction effect can be detected as an intensity change.